Rotary pump and motor hydraulic transmission



Jan. 15, 1957 AG. BADALINI 2,777,286

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION Filed May l2, 1953 United States Patent O ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION Giovanni Badalini, Milan, Italy, assignor to S. p. A. Cambi Idraulici Badalini, Rome, Italy Application May 12, 1953, Serial No. 354,609 Claims priority, application Italy August 6, 1952 2 Claims. (Cl. 611-53) The invention relates to variable speed variable torque power transmission apparatus for transmitting power from a driving element to a driven element and employing a liquid as the power transmission medium.

The apparatus of the invention is of the type comprising a multi-cylinder pump and a multi-cylinder motor hydraulically connected to each other, wherein the cylinders of the motor surround the cylinders of the pump and are concentric therewith and wherein the pump cylinder body is fastened to the driving shaft and the motor cylinder body is fastened to the driven shaft and the pump piston rods are rotatably supported by a plate inclined at a fixed angle with respect to the driving shaft whereas the motor piston rods are rotatably supported by a swash plate having an inclination variable at will from the outside of the apparatus.

The apparatus of the invention is characterised in that the distribution of the liquid, preferably of the oil, to the cylinders of the motor is controlled by a ring valve plate eccentrically mounted at one end of a stationary spindle arranged inside the driven shaft and a valve is mounted inside said stationary spindle and hand-operable to place in short circuit the cylinders of the pump with those of the motor to render independent of the driven shaft the rotation of the driving shaft.

One form of the apparatus of the invention is illustrated in the accompanying drawing wherein:

Figure 1 is a longitudinal section through the apparatus ,arranged for installation in a motor vehicle of low power;

Figure 2 shows a detail of the distribution of the liquid to the cylinders of the apparatus of Fig. 1.-

The apparatus referred to comprises a pump unit A and a motor unit B of the swash plate type each of which is formed of a plurality of cylinders.

The pump and the motor are hydraulically interconnected in a closed circuit and the cylinders of the pump are co-axial with and arranged radially in the cylinder block of the motor.

At one end of the driving shaft 1, a gear R1 is mounted which is made to rotate by a suitable prime mover. On the driving shaft. 1 is keyed the body 2 of the pump cylinders.

In the cylinders of the pump A the pistons 3 reciprocate and at one end abut, through the slippers 4, a backing plate 5, which is supported by the end block 6. f

The cylinder body 2 of the pump bears on the distributing plate 7. The cylinder body of the motor is arranged about the cylinder body 2 of the pump and fastened to the end block 6 of the pump and to the distributing plate 7. The cylinder block 10 is further fastened to the casing portion 8 which carries the driven shaft 9 of the apparatus; on the shaft 9 a gear R2 is keyed for connection with the wheels of the motor vehicle. i The cylinder body 10 of the motor together withthe yend block 6 and the casing portion 8 forms an assembly fastened to and rotating with the driven shaft 9 which rotates with respect to the cylinder body 2 of the pump.

'Ilie slippers 11 of the pistons 12 of the motor cylinders i 2,777,286 Ce Patented Jan. 15, k1 957 abut on the ring 13 which bears, by means of balls or rollers, on the swash plate 14. The latter is pivoted at its sides on the housing 15 of the apparatus by means of two pivots (not shown) the axis of which lies under the longitudinal axis O-O of the apparatus. The inclination of the swash plate 14 is controlled by the piston 16 which reciprocates inside a cylinder 20, made in the housing 15. The driven shaft 9 is axially bored to receive a spindle 17 one end of which is keyed to the stationary flange 18 by means of pin 37 and at the other end eccentrically carries the distributing ring valve 19 (Fig. 2) which controls the distribution of the oil to the cylinders of the motor.

The eccentric of spindle 17 is provided with two bores 38 which permit the passage of the oil when a valve 22 (to be described later) is removed from its seat.

In the distributing plate 7 there are provided two ports and namely an output port 32 and a suction port 31 for the pump. These ports communicate with a chamber 28 formed between the distributing plate 7 and the casing portion 8. The chamber 28 is divided into two portions by the distributing ring valve plate 19 and namely an inner portion 29 and an outer portion 30. The port 32 communicates with the portion 29 of chamber 28 through the duct 26 and the port 31 communicates with the portion 30 of chamber 2S through the duct 27.

In the distributing plate 7 there are also provided for each cylinder the ducts 34 and 33 which connect the chamber 28 with the cylinders of the motor B.

The axis W-W of the distributing ring valve plate lies in the plane including the axis O O and the axis of the pivots (not shown) of plate 14. In this plane, the axis W-W is spaced apart from the axis O O and is parallel thereto.

Due to the eccentricity of ring valve plate 19, the inlet ports 33 of thecylinders of the motor B and the output ports 32 of the cylinders of the pump A communicate with the inner portion 29 of chamber 28, and the output ports 34 of the cylinders of the motor and the suction ports of the cylinders of the pump communicate with the outer portion 30 of the chamber 28.

The operation of the apparatus is the following. As-

suming the swash plate 14 of the motor B to be in the position shown in Fig. l, when the driving shaft 1 rotates a certain amount of oil through the output port 32 of the pump A, the duct 26, the portion 29 of chamber 28 and the duct 33 acts upon the input side of the motor B, causing the cylinder block 10 of the motor to rotate. Together with the cylinder block 10 of the motor also the end block 6, the casing portion 8, and the driven shaft 9 fastened to the latter rotate. In consequence of said rotation the volumetric displacement of the pump A is no more proportional per minute of the driving shaft. 1 but said volumetric displacement is proportional to the difference between the revolutions per minute of the driving shaft 1 and the revolutions per minute of cylinder body ofthe motor, thus imparting to the driven shaft 9 a rotatory speed which corresponds to the given inclination of the swash plate 14 in Fig. 1. By varying the inclination of the swash plate 14 the volumetric displacement of the motor cylinders is varied and hence the amount of oil entering the motor, thus varying the transmission ratio of the apparatus. v

If the speed of the driving shaft 1 is kept constant, the speed of the driven shaft 9 will depend only upon the inclination of the swash plate 14 that is upon the ratio of the volumetric displacement of the motor B and that of the pump A. At the limit, when the volumetric displacement of the motor B is zero the transmission ratio will be 1:1 and the driving shaft 1 and the driven shaft 9 rotate in synchronism. In the intermediate positions the higher the inclination of the back plate 14 of the motor the higher is the transmission ratio.

The specific value of the volumetric displacements will only alect, the pressure being equal, the torque transmitted.

The torque available on the driven shaft 9 is the sum of the reaction torque of the pump and of the torque due to the motor. The tirst torque is given by the reaction engendered by the pump casing by the elements of the pump rotating with the driving shaft and this torque is invariable for any transmission ratio. The second torque is that one engendered by the motor in virtue of the oil which the motor receives from the pump and this torque varies from zero to a maximum value according to the inclination of plate 14.

As already stated, the inclination of the swash plate 14 may be varied by means of the cylinder 20 by introducing therein or removing therefrom oil by means of a device not shown, which will not be described in detail.

When the swash plate 14 is in the position corresponding to the transmission ratio 1:1, that is when the volumetric displacement of the motor B is equal to zero (swash plate 14 perpendicular to the axis of the driving and driven shaft) there is no passage of oil from the pump to the motor.

The cylinder body of the pumps rotate together with the cylinder body of the motor and the parts connected thereto, and the thrust due to the pump pistons is received by the corresponding supports without causing losses of power.

In the motor B, on the contrary, the thrust of the pistons at one side are balanced by the pressure existing inside the 'chamber 29, and at the other side are received by the thrust bearings of plate 14.

The variable speed transmission apparatus disclosed is particularly suitable for motor vehicles of low power since the apparatus may be kept within very small dimensions particularly in longitudinal direction, although permitting the cylinders of the motor to have ya. noticeable length. The volumetric displacement being equal, in this apparatus there are decreased thrusts upon the ring 13 of the motor B without being compelled to impart excessive inclination to the swash plate 14.

The yield is high especially when working at a transmis sion ratio near to 1:1 which is the most frequent in motor vehicles of low power.

In order to permit the driven shaft to become idle, a valve 22 is provided to bypass the inlet and the outlet of the pump through the bores 38 made in the eccentric of spindle 17. The valve 22 is axially bored to equalize the pressure at the two ends of the valve, thus avoiding the necessity of making use of a very strong spring to reseat the valve. The valve 22 is biased toward its seat by the spring 23, so that to unseat the valve it is necessary to exert a pulling force on the shank 24. By releasing said shank suddenly the valve closes slowly and the reengageinent of the driven shaft to the driving shaft takes place gradually since valve 22 has iirst to annul the dynamic thrust of the uid coming out from the bypass opening.

The pump P has the purpose of returning the 'oil which leaks from the apparatus into circuit through the bore of shaft 1 and the ball valves 35 and 36. Said valves allow the oil to return under low pressure into the transmission circuit, at the suction side, so that to prevent the forming of air bubbles and also to cause the pistons to move back without making use of springs or like devices, since they ensure the continuous abutment of the pump pistons against thebacking plate during the suction phase.

What I claim is:

1. Hydraulic variable speed transmission suitable for tractlon purposes on small power motor `vehicles par-r ticularly on two-wheel motor vehicles comprising a driving shaft and a driven shaft, a hydraulic multi-cylinder pump having the cylinder body which rotates with the driving shaft, a hydraulic multi-cylinder motor having the cylinder body which rotates with the driven shaft, the cylinder body of the motor surrounding the cylinder body of the pump and being concentric therewith, a

stationary housing containing said multi-cylinder pump and motor, said pump and said motor being hydraulically interconnected in a closed circuit, a distributing valve plate interposed between the cylinder bodies of the pump and motor, said valve plate receiving in abutment the pump cylinder body and being fastened for rotation to the motor cylinder body, pistons reciprocating in the cylinders of the pump and motor, inlet and outlet ports for the liquid in the cylinders of the pump and motor, a first cap fastened to the motor cylinder body and having an inclined bottom against which the pump pistons abut for rotation, a swash plate pivoted to the stationary housing and receiving in rotatory abutment the motor cylinder pistons, a second cap fastened to the motor cylinder body opposite to the first cap, said second cap being provided with an extension axially bored and in the form of a driven shaft, the driving and the driven shaft each being journalled at one side of the stationary housing, said distributing valve plate and said second cap facing each other and being spaced apart from each other to form is distribution chamber for the liquid, the driving shaft being provided with an axial duct, an auxiliary pump mounted on the driving shaft to supply liquid under pres sure to the hydraulic circuit of the multi-cylinder pump and motor through the said axial duct of the driving shaft, a spindle axially bored and located in the said bored extension of the second cap and provided at one end with an eccentric, a distributing ring valve for the oil to be conveyed to the motor mounted on the said eccentric, said ring valve being contained in the said distribution chamber and abuting against the said distributing valve plate and dividing the said distributing chamber in an inner and an outer portion, ducts in the said distributng valve plate which communicate the pump cylinders with the motor cylinders through the inner and the outer portions of the distribution chamber, the distributing ring valve being provided with radial ducts which communicate the said inner and outer portions of the distribution chamber, a spring biased stem valve slidably contained in the said axially bored spindle to keep closed the radial ducts of the said ring valve, said stem valve being axially bored to equalize the pressure at the two ends of the valve and being operable to open said radial duct against the action of the spring to by-pass the inlet and the outlet ports of the pump cylinders.

2. Hydraulic variable speed transmission as claimed in claim l, 'wherein the outlet ports of the pump cylinders and the inlet port 'of the motor cylinders communicate with the inner portion of said distribution chamber, and the outlet ports of the motor cylinders and the inlet ports ofthe pump cylinders communicate with the outer portion of the distribution chamber, and wherein the distribution plate valve is further provided with ducts which put in communication the axial duct of the driving shaft with the hydraulic circuit of `the multi-cylinder pump and motor, a valve ball being provided in each of the said last mentioned ducts of the plate valve.

References Cited in the le of this patent UNITED STATES PATENTS 1,348,738 Rayburn et al Aug. 3, 1920 1,726,454 Rayburn et al Aug. 27, 1929 1,840,864 Rayburn et al. Jan. 12, 1932 1,840,865 Rayburn et al. Jan. l2, 1932 

